(1) Field of the Invention
This invention relates generally to helmets for use in high temperature environments, and more particularly to the monitoring of hazardous ambient thermal conditions of such helmets. The expression "ambient thermal condition of a helmet" as used in the context of the present invention, the present specification and the appended claims, is used to define the thermal condition within the helmet and the thermal condition immediately adjacent the exterior of the helmet, such as the thermal condition immediately adjacent the exterior surface of the helmet and the thermal condition immediately adjacent a face shield or facepiece mounted pivotally to the top front portion of the helmet.
(2) Description of the Prior Art
Most helmets are worn to protect the head from impact forces which may be encountered in many different types of activity, including activities which are performed in high temperature environments. Firefighting is one such activity in which a very severe high temperature environment is encountered. Although firefighting assembly is available for monitoring an accumulative thermal condition and time of exposure thereto, this accumulative thermal condition does not necessarily relate directly to the ambient thermal conditions of the helmet which are encountered within helmets and immediately adjacent the exterior of the helmets that are worn during firefighting activities.
To greatly reduce the weight of helmets, reinforced plastic is commonly utilized as the material in the impact protecting shell portion of most helmets. Since the integrity of plastic deteriorates at elevated temperatures, a need exists for the ambient thermal condition of the helmet shell to be monitored directly. Furthermore, high temperature buildup within a helmet diminishes alertness and can even cause unconsciousness, so that a need also exists for the temperature buildup within helmets to be monitored directly. Of course, such thermal monitoring needs exist not only for helmets worn in firefighting but also for helmets worn in other activities, such as those of workers in a steel mill, and similar monitoring needs where surrounding environment temperature would be excessive.